Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity. In use, the electrode catheter is inserted into a chamber of the heart. Once the catheter is positioned, the location of aberrant electrical activity within the heart is then located.
One location technique involves an electrophysiological mapping procedure whereby the electrical signals emanating from the conductive endocardial tissues are systematically monitored and a map is created of those signals. By analyzing that map, the physician can identify the interfering electrical pathway. A conventional method for mapping the electrical signals from conductive heart tissue is to percutaneously introduce an electrophysiology catheter (electrode catheter) having mapping electrodes mounted on its distal extremity. The catheter is maneuvered to place these electrodes in contact with or in close proximity to the endocardium. By monitoring the electrical signals at the endocardium, aberrant conductive tissue sites responsible for the arrhythmia can be pinpointed.
Once the origination point for the arrhythmia has been located in the tissue, the physician uses an ablation procedure to destroy the tissue causing the arrhythmia in an attempt to remove the electrical signal irregularities and restore normal heart beat or at least an improved heart beat. Successful ablation of the conductive tissue at the arrhythmia initiation site usually terminates the arrhythmia or at least moderates the heart rhythm to acceptable levels.
A typical ablation procedure involves providing a reference electrode, generally taped to the skin of the patient. RF (radio frequency) current is applied to one or more electrodes on the tip of the catheter, and current flows through the media that surrounds it, i.e., blood and tissue, toward the reference electrode. Alternatively, the catheter may carry bipolar electrodes, in which instance, the current flows from one tip electrode, through the media and toward another electrode carried on the catheter tip. In any case, the distribution of current depends on the amount of electrode surface in contact with the tissue as compared to blood, which has a higher conductivity than the tissue. Heating of the tissue occurs due to electrical current. The tissue is heated sufficiently to cause cellular damage in the cardiac or vascular tissue resulting in formation of a lesion which is electrically non-conductive.
Catheters with multiple spines (commonly referred to as “flower catheters”) are known. With each spine carrying at least one electrode, simultaneous contact with multiple locations at a tissue target site is possible for expediting mapping and ablation, especially in a tubular region when lesions or a “line of block” is desired around an inner circumference of the tubular region to interrupt wavelets originating from the tubular region or vessel. With spines having uniform length and arranged in a radial pattern, tissue contact along an inner circumference of the tubular region or vein is readily achieved. A more continuous inner circumference is readily achieved with rotation of the catheter. However, it has been found that ablation along an inner circumference or a narrow band in a vein can lead to vein stenosis, including narrowing, tightening or stiffening of the vein.
Moreover, vessel anatomy comes in all shapes and sizes. Vessel diameters can vary greatly, and abnormally-shaped vessels are sometimes encountered. In these situations, a flower catheter that permits adjustability in the arrangement and positioning of the spines would greatly reduce the time required for perform mapping and/or ablation.
Thus, there is a desire for a catheter adapted for mapping and ablation in a tubular structure that can map or ablate a tubular region which will reduce undesirable damage to the tubular structure. There is a further desire for a flower ablation catheter to provide simultaneous tissue contact to form a line of block without causing stenosis and allow adjustability in the arrangement and/or positioning of the spines.